What's at stake

South Ossetia is claimed by Georgia, the former Soviet republic that cast its lot with the West to the irritation of Moscow. The breakaway province has been under Russia's sway for years. Georgia sits shoulder to shoulder with huge Russia, not far from Iran, and astride one of the most important crossroads for the emerging wealth of the rich Caspian Sea region.

A U.S.-backed oil pipeline runs through Georgia, allowing the West to reduce its reliance on Middle Eastern oil while bypassing Russia and Iran.

The dispute makes the Bush administration the middleman between an ally -- Georgia contributes combat troops for Iraq and counterterrorism intelligence -- it wants to help and the powerful former adversary next door whose help it needs with Iran and North Korea.

The 1,100-mile pipeline carries oil from Azerbaijan's Caspian Sea fields, estimated to hold the world's third-largest reserves. Most of the oil is bound for Western Europe. However, what the pipeline carries affects prices elsewhere.

South Ossetia is one of the few places where ethnic, nationalist or other complications from the Cold War went dormant but didn't die. U.S diplomats refer to these squabbles as "frozen conflicts," a euphemism that belies the long-recognized threat that seemingly petty disputes can easily provoke war. Here's a look at the conflicts:

Georgia-South Ossetia: South Ossetia is an enclave of 70,000 people bordering Russia. One-third of its population is Georgian. Ossetians seek union with North Ossetia, which is inside the Russian Federation.

Georgia, whose 4.4 million people speak Georgian and Russian, voted for independence after the former Soviet Union disintegrated in 1991. Ethnic clashes erupted in 1989 as the Soviet Union headed toward breakup and unrest continued after Ossetian leaders declared their intention to secede.

South Ossetia, which receives political and economic support from Russia, voted to secede in 2006, but the referendum wasn't internationally recognized. The dispute became enmeshed in the larger tensions between the United States and Russia over the expansion of NATO, which Georgia is seeking to join.

Georgia-Abkhazia: Georgia also is grappling with breakaway Abkhazia, a region of about 250,000 people on the Black Sea whose separatist leaders receive strong backing from Moscow. Ethnic Georgians were a majority of the population there when the Soviet Union collapsed and Georgia became independent. Ethnic Abkhaz began agitating for independence and fighting erupted, prompting Georgia to send in troops.

Moldova-Trans-Dneister: Trans-Dneister, most of whose population speaks Russian and Ukrainian, declared independence in 1990 from Moldova. The declaration has never been recognized internationally. NATO has demanded that Russia withdraw its troops from Trans-Dneister. But Moscow continues to maintain a base there.

Nagorno-Karabagh: The enclave, whose population is mainly ethnic Christian Armenian, sit in the overwhelmingly Muslim former Soviet republic of Azerbaijan. Ethnic clashes erupted in 1988, prompting ethnic Azeris to flee the enclave and Armenia, and ethnic Armenians to flee Azerbaijan.

The number of displaced people is estimated at 1 million. Up to 30,000 people are thought to have died before Russia brokered a 1994 cease-fire. Internationally mediated talks between Azerbaijan and Armenia have failed to resolve the dispute.